The chemical composition of polyacrolein (PA) microspheres of various types as well as polyglutaraldehyde (PGL) microspheres was elucidated. Nephelometric measurements were used for studying the stability properties of the polyaldehyde microspheres in different pH and salt concentrations. The stability of the aldehyde groups themselves at various pH and temperature was also determined. The polyaldehyde microspheres covalently bind amino ligands, e.g., proteins, antibodies, enzymes, and drugs in a single step. The effect of temperature and the influence of thiol compounds on the reaction between the polyaldehyde microspheres and amino ligands was examined. The reaction of the polyaldehyde microspheres with sodium hydrogen sulfite is also described. 相似文献
Summary: Suspension polymerization yielded microspheres (40–50 μm) of polyacrolein. Smooth and rugged surfaces can be created by varying the polymerization procedure. We have shown that the polyacrolein resins with a high loading of aldehyde groups serve as effective scavengers for primary amines and may be used to remove compounds bearing amino groups in the combinatorial synthesis of compound libraries. Copolymerization with styrene can help to separate the adjacent aldehyde groups, thus making the functional groups more available in organic reactions. The polyacrolein resins in the aldehyde form or after appropriate chemical modifications may also be useful as support materials in solid‐phase synthesis.
The SEM image of macroporous polyacrolein microspheres with toluene as porogen prepared by free radical polymerization. 相似文献
Polymeric microspheres of methyl methacrylate (PMMA) have been prepared via emulsion polymerization using potassium persulfate as initiator. The polymeric spheres were also prepared with varied concentration of an additional component, 2-vinyl-4,4′-dimethylazlactone (VDMA), which greatly affected the properties of the spheres. NMR analysis indicates the presence of VDMA in the polymer particles, and FT-IR analysis shows hydrolysis of VDMA in the polymer which produced N-acryloylmethylalanine, (NAMA). The VDMA hydrolysis thus led to carboxyl functionality which served to stabilize the microspheres during the emulsion polymerization showing a significant effect on particle size, distribution, and morphology, but little effect on molecular weight or thermal properties of the polymer. Also the effect of varying the concentration of initiator (potassium persulfate, KPS) was investigated, and had little effect on particle size or distribution or molecular weight of the polymer particles. 相似文献
Uniform inorganic- (PbS) coated polymer core-shell and hollow PbS microspheres were prepared by an easy and economical approach.
Monodisperse polystyrene (PS) microspheres were used as templates, as well as the core of the composite spheres; lead sulfide
shells were obtained through the reaction of lead acetate (Pb(CH3COO)2) and thioacetamide (TAA) at room temperature. The morphologies and structures of the as-synthesized products were systematically
characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray powder
diffraction (XRD), and Fourier transform infrared spectra (FTIR). The fluorescence property of the as-synthesized product
was also investigated. A reasonable mechanism for the formation of PS–PbS core-shell and hollow PbS microspheres was discussed.
According to a series of parallel experiments, effects of related experimental parameters were also carefully investigated,
such as the molar ratio of Pb(CH3COO)2 to TAA, reaction temperature, etc. 相似文献
The polystyrene (P(S)), poly(styrene/acrolein) (P(SA)), and polyacrolein (P(A)) latexes, with varied fraction of polyacrolein in the surface layer (fA=0, 0.50, 0.63, 0.84, 1.00), were used for the attachment of horseradish peroxidase. Surfaces of latexes were modified by reaction with ethylenediamine. In this step the aldehyde groups from polyacrolein were blocked and the primary amino groups were introduced. The carbohydrate portion of HRP was oxidized in the reaction leading to formation of aldehyde groups. The adsorption and covalent immobilization of HRP onto the P(S), P(SA), and P(A) latexes and of the oxidized HRP (HRP-OX) onto the modified latex particles, with amino groups on the surface (P(SA)-M and P(A)-M), were investigated. The activities of parent and oxidized HRP were compared with activities of the corresponding enzymes in solution. It has been found that whereas HRP is not suitable for the covalent immobilization on P(SA) latex and loses its activity after adsorption onto P(S) latex, HRP-OX can be adsorbed onto P(S) latex and is readily immobilized covalently onto the ethylenediamine modified P(SA) and P(A) latexes, retaining much of its former enzymatic reactivity.This work was supported by the KBN Grant 2 0624 91 01 相似文献
Narrow-disperse magnetic microspheres were prepared by alkaline coprecipitation of Fe2+ and Fe3+ ions within poly(acrylic acid–divinylbenzene) microspheres that were prepared by distillation–precipitation copolymerization. Magnetic microspheres with polymer brushes that contain epoxy groups were prepared by graft copolymerization of glycidyl methacrylate and glycerol monomethacrylate via atom transfer radical polymerization (ATRP) from the magnetic microsphere surfaces. Subsequently, magnetic microspheres with thiol-containing polymer brushes were prepared by treating the epoxy group-containing magnetic microspheres with sodium hydrosulfide. Gold nanoparticles were immobilized in the brush layer of the thiol-containing magnetic microspheres through Au–S coordination. The catalytic activity of the gold nanoparticle-immobilized magnetic microspheres was investigated using the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as a model reaction. The catalyst could be reused for over 10 cycles without noticeable loss of catalytic activity. 相似文献
The graft polymerizations of acrolein (AL) onto an imidazole (Im)-containing polymer, such as a homopolymer of 4(5)-vinylimidazole (VIm) and several copolymers of VIm-4-vinylpyridine (VPy), VIm-1-vinyl-2-pyrrolidone (VPr), and VIm-styrene (St), have been studied in ethanol at 0°C. The degree of polymerization (P?n) of the resulting polyacrolein graft depended on the number of Im units in the Im-containing polymer which produced a decrease in P?n of grafted polyacrolein. The P?n of the graft polyacrolein was determined to be in the range of 5-23. The rate of polymerization (Rp) was expressed by Rp = k(PVIm) (AL)2. The graft polymerizability of the AL was influenced by the comonomer in the parent polymer, and was found to be in the order of VIm homopolymer > VIm-VPr copolymer > VIm-VPy copolymer > VIm-St copolymer. Rp was affected by the functional group around the Im group in the Im-containing polymer. These results were discussed by assuming the conformation of the parent polymer in ethanol. 相似文献
The thermally reversible photocyclization of α-p-dimethylaminophenyl-N-m-nitrophenylnitrone (I) to the corresponding oxaziridine (II) was studied in solution and in rigid polymer matrices. Irradiation with light of wavelength above 380 nm causes a clean transformation of (I) to (II) in solution as well as in polymer matrices. The quantum yield of the photoreaction in solution is about 0.06, the value being almost independent of the nature of the solvent and the irradiation time. In poly-(methyl methacrylate) (PMMA) and in polystyrene (PSt) films, the photocyclization shows initial quantum yields of 0.1 and 0.23, respectively, which decrease with irradiation time. In solution in the dark, II reverted mainly to I with formation of side product(s) in a first-order reaction. The recovery of I during the dark reaction (60–90%) as well as the rate constant of the reaction are strongly affected by the solvent. The kinetics of the thermal return in the two polymer matrices does not follow the first-order rate law. The initial reaction rate as well as the extent of the recovery of I in PMMA film are greater than those in ethyl acetate. 相似文献
Poly[acryloyl-L-valine (ALV)] microspheres containing peroxy ester groups were prepared by radical copolymerization of ALV with a small amount of di-tert-butyl peroxyfumarate. When the microspheres were irradiated in the presence of second vinyl monomers, long-lived propagating radicals of the second monomers were formed in the microspheres by the reaction of microsphere polymer radicals with the monomers. The presence of a minute quantity of ethyl alcohol served to soften the microspheres and made the polymer radicals more mobile in the microspheres. As a result, sharper ESR spectra of the propagating radicals were observed although their lifetimes became shorter. This microsphere method also yielded easily the stable propagating radicals of a-methylstyrene and 1,1-diphenylethylene which have no homopolymerizability in usual radical polymerization. When N-n-propyldimethacroylamide and N,N′-dimethyl-N,N′-dimethacroylhydrazine, which undergo cyclopolymerization, were used as second monomer, uncyclized polymer radicals were only observed. Some discussions were given on the propagation mechanism of the cyclopolymerization. 相似文献
Through a “one-pot” strategy, a layer of microporous organic polymer was coated onto the surface of monodisperse amino-functionalized silica microsphere via amino-aldehyde condensation reaction with core-shell structure. The change in chemical structure of material before and after modification was determined by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Due to existence of a large number of amino and aldehyde groups in microporous organic polymer shell, the water contact angle decreased from 56.8° (silica microspheres) to 34.7° (microporous organic polymer-coated silica microspheres). Based on these properties, microporous organic polymer-coated silica microspheres were employed as the stationary phase for capillary liquid chromatography and successfully offered baseline separation of polar small molecules. Additionally, the material could also be served as the sorbent of hydrophilic interaction chromatography to enrich glycopeptides from human serum digest. A total of 470 unique N-glycopeptides and 342 N-glycosylation sites mapped to 112 N-glycosylated proteins were unambiguously identified from 2 μL of human serum, exhibiting a promising application prospect of microporous organic polymer-coated silica microspheres in the pretreatment of proteomics samples. 相似文献
Highly crosslinked narrow or monodisperse poly(ethyleneglycol dimethacryltae) (polyEGDMA) microspheres were prepared by distillation-precipitation polymerization in neat acetonitrile with 2,2′-azobis(2-methyl propinitrile) (AIBN) as an initiator. The polymer microspheres with clean surfaces due to the absence of any added stabilizer in the reaction system were formed simultaneously through a precipitation manner during the distillation of acetonitrile off the reaction system. The effects of the solvent, initiator concentration, monomer concentration and comonomer (divinylbenzene, DVB) fraction on the formation of the microspheres were investigated. Narrow- or monodisperse particles with spherical shape and smooth surface were obtained with diameters between 1.18 and 2.50 μm with monomer loading lower than 3.13 vol%. The surfaces of the microspheres became rougher, some elliptic particles and doublet or triplet appeared with the increase of monomer concentration (as high as 3.75 vol%). The yield of polymer microspheres was increased from 31% to 75% with the increase of EGDMA fraction from 0 to 100% when EGDMA was copolymerized with DVB. The resulting polymer microspheres were characterized with scanning electron microscope (SEM) and Fourier transform-IR spectra. 相似文献
Monodispersed TiO2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA). The effects of the APA:TTIP molar ratio, water content, reaction time and reaction temperature on the morphology of the resultant spheres were investigated. The products were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was demonstrated that the diameters of the resultant TiO2 spheres could be tuned in the range of 380–800 nm by changing the APA:TTIP molar ratio (1:3 to 3:1) and water content (1–3 v/v%) in the reaction medium, and that increasing the APA:TTIP molar ratio led to larger TiO2 hybrid spheres while increasing the water content decreased their size. The loading content of APA in the hybrid spheres could reach 20 wt.% as they were prepared with the APA:TTIP ratio of 3:1. The possible formation mechanism of the hybrid spheres was also investigated. It was found that APA slowed down the hydrolysis rate of the titanium precursor so that resulted in the formation of the TiO2 spheres. In addition, the APA present in TiO2 spheres acted as a reducing agent to in situ convert HAuCl4 into metallic Au on the surface of the TiO2 spheres. The catalytic activity of the resultant Au/APA–TiO2 composite was examined using transfer hydrogenation of phenylacetone with 2-propanol, and it was indicated that the catalyst displayed high efficiency for this reaction. 相似文献